Scientists recorded rig sharks producing soundspotentially with their teeth. The clip is thought to be the first documentation of its kind. Paul Caiger / University of AucklandScientists have long thought that sharks roam the ocean in silence. But now, a new recording is challenging that assumption.A team of researchers captured strange clicking noises from the rig shark, a small species that lives off the coast of New Zealand. To the best of our knowledge, this study would be the first to show that sharks can produce sounds, they write in their paper, published Wednesday in the journal Royal Society Open Science.The findings suggest audible noises play a bigger role in sharks experience than scientists had previously imagined. Sharks have sensory systems that are more refined than their hearing, like their electroreceptors, their smell and the way they propel themselves through the water, says lead author Carolin Nieder, a researcher at the Woods Hole Oceanographic Institution, to Live Sciences Jacklin Kwan. But I think the original notion that we had that sound isnt important at all is also likely not true.Nieder first heard the sounds by accident in 2021, while she was conducting her PhD research at New Zealands University of Auckland. She noticed that the rig sharks she was studying would start to make a chirping noise when she handled them in between tests in the lab. When I first heard the sound, I thought they sound like electric sparks, Nieder says to the Australian Broadcasting Corporations Peter de Kruijff.At first we had no idea what it was, because sharks were not supposed to make any sounds, says Nieder to Jack Tamisiea at Scientific American. I remember coming home and just thinking more and more about how weird those sounds were.Nieder couldnt investigate the sounds further at the time, but she remained curious. In the new research, she studied ten juvenile rig sharks kept in the lab between May 2021 and April 2022 to better understand the mysterious crackling noises.The researchers individually transferred each shark into a tank equipped with recording devices. One at a time, a scientist held the animals for 20 seconds.As the sharks were moved, they began to make short clicking soundseach lasted only around 48 milliseconds. But the noises were loud: Their volume reached above 155 decibels, which is comparable to a shotgun. The clicks were mostly single pulses, but roughly a quarter happened in pairs. About 70 percent of the sounds were accompanied by a calm, swaying body movement, while 25 percent came with vigorous thrashing of the head or body. The other 5 percent occurred while the shark was still.The researchers also noted that the sounds were more frequent in the first ten seconds of the handling sessions. As the animals got used to the daily experimental protocol, they then stopped making the clicks altogether, as if they got used to being in captivity and the experimental routine, Nieder says in an email to CNN. This led us to consider that maybe we are observing a sound-making behavior rather than a strange artifact.Notably, the frequencies of the sounds were too high for the rig sharks hearing range. This suggests the animals arent emitting the noise to communicate with each other. The scientists arent entirely sure what the purpose of the sound is yet, they write in the study, but it could perhaps serve as a defense against predators. Several species of toothed whales, which hunt rig sharks, would be able to hear the sounds.Its too early to tell whether its a response, kind of saying, go away, or if [its] just their nervous system is firing off, which just happens to make their teeth and jaws click, Adrian Gutteridge, a shark biologist with the International Union for Conservation of Nature who was not involved in the study, says to Live Science.Many fish use their swim bladder to make noisea gas-filled organ that helps with buoyancy and allows the animals to communicate. But sharks dont have this organ, and scans of the rig sharks found no other possible sound-producing body parts. The study suggests the sound is coming from the sharks teeth instead, but only direct, up-close observation of the jaws would definitively prove or disprove that hypothesis.The researchers also note that more research will be needed to determine whether the sharks would behave the same way in the wild. The open question is, Would the sharks make the noises in more natural circumstances? says marine biologist Dennis Higgs of the University of Windsor in Canada, who was not involved in the research, to Scientific American.Get the latest stories in your inbox every weekday.Filed Under: Animals, Biology, Communication, Fish, New Research, Oceans, Sharks, Sound Recordings